Inadequacy of FDA dosing guidelines for intravenous theophylline

The ability of a dosing regimen of intravenous theophylline to achieve therapeutic serum theophylline concentrations was evaluated. Intravenous theophylline was administered to 25 adult patients with acute bronchospasm using dosing guidelines 20 percent higher than FDA recommendations. The dose of theophylline was determined by assignment to one of four clinical categories. Blood samples for determination of serum theophylline concentrations were collected 12 and 24 hours after initiation of a constant infusion. Differences between mean observed and target theophylline concentrations did not achieve statistical significance. All patients in categories 1 and 2 achieved therapeutic concentrations of theophylline. Most of those with subtherapeutic levels were smokers suffering from multiple diseases. We conclude that current FDA recommendations for dosing intravenous theophylline are unreliable for routine use in category 3 and 4 patients. Further work is necessary to evaluate these recommendations in pediatric and category 1 and 2 patients.